While cellular reprogramming is generally utilized for applications in stem cell biology and regenerative medicine, this approach can also be used as the basis for genetically-engineered models of human disease, including cancer. In particular, we propose that directed lineage conversion/transdifferentiation can be used in combination with gene targeting methods for the creation of novel models of human cancer. In this application, we will use reprogramming of fibroblasts together with tissue recombination and CRISPR-mediated gene targeting to generate mouse and human prostate tissue for modeling of prostate cancer. In our preliminary studies, we have shown that mouse fibroblasts can be reprogrammed to prostate tissue using a three-step process involving transient induction of pluripotency factors, expression of transcriptional regulators of prostate epithelium, and tissue recombination with urogenital mesenchyme followed by renal grafting. Based on our preliminary findings, we hypothesize that this reprogramming approach can be used in combination with CRISPR-mediated gene targeting of tumor suppressor genes to generate novel genetically-engineered human models of prostate cancer. We will now investigate the generation of human models of prostate cancer using two specific aims: (1) Investigation of reprogramming of human fibroblasts into prostate epithelium to identify optimal conditions for specification of prostate epithelial differentiation and by molecular analyses of reprogrammed prostate tissue; and (2) Modeling of human prostate cancer by gene targeting and reprogramming using CRISPR-mediated gene targeting for the specific alteration of tumor suppressor genes that are mutated in human prostate cancer, followed by generation of reprogrammed human prostate tissue that has undergone oncogenic transformation. In combination, these studies will provide the basis for an innovative approach for human cancer modeling, which should yield important new insights into the molecular mechanisms of human prostate cancer initiation and progression.